Each MR should ideally have its corresponding tests
The second commit does add conformance tests in `dlls/wintypes/tests/propertyset.c` and should cover all `IPropertySet` methods.
~5 patches or so for an MR would be best.
Right, but I'm not sure how to organize this into two MRs. Would it be acceptable for the first MR to only contain the stubs for the `I{Observable}Map`, `IMapView`, `IIterable` and `IIterator` interfaces (i.e, the first 9 commits)? The tests have been appropriately todo-ed and "untodo-ed" for every new feature added in a commit, so it does pass the tests.